Abstract Quadriceps weakness develops rapidly after anterior cruciate ligament (ACL) injury and surgery. Despite aggressive rehabilitation, most people have noteworthy quadriceps weakness when they return to activity. This persistent quadriceps weakness has been associated with altered gait patterns, reduced functional performance, and poor long-term knee health-related quality of life. Emerging evidence also indicates that quadriceps weakness plays a crucial role in the development of post-traumatic osteoarthritis ? a negative outcome that is inevitable in almost 50% of this population. Thus, there is a pressing need for new, clinically- feasible intervention strategies to improve quadriceps function after ACL injury and surgery. We hypothesize that a lack of task-specific training elements in current rehabilitation approaches is the underlying reason for the inability to optimally address persistent asymmetry in knee strength and gait after ACL surgery. Accordingly, the current proposal aims to improve quadriceps function in individuals with anterior cruciate ligament (ACL) reconstruction via a novel paradigm, termed as functional resistance training. Progressive functional resistance training will be performed during walking for 8-weeks using a low-cost wearable robotic brace that is capable of providing scalable resistive torques. Various knee-related biomechanical, neuromuscular, and clinical outcomes will be evaluated both before and after the intervention, and will be compared with a dose-matched control group. The effects of progressive functional resistance training during gait on cortical and spinal reflex excitability will also be evaluated to understand the mechanistic underpinnings of improvements mediated by the intervention. The results of the proposed studies will establish the feasibility of functional resistance training to normalize biomechanical and neuromuscular profiles in individuals with ACL reconstruction. More importantly, the proposed application, if successful, may serve as a foundation for a novel paradigm to target quadriceps dysfunction in individuals with a wide range of knee injuries.